This invention relates to novel non-ionic urethane monomers and emulsion and solution polymers and copolymers comprising the non-ionic urethane monomers. The polymers comprising these novel monomers thicken, modify theology, stabilize, suspend particles, control viscosity and otherwise enhance the physical properties of latex systems, coating compositions, sizings and printing pastes, paints, paper coatings, industrial coatings, petroleum drilling fluids, cleaners, detergents, personal care products and other aqueous solution or emulsion products.
Various polymeric materials based on mono and dicarboxylic acids are known. The properties of these polymers, in particular, the thickening efficiency of these polymers, has been improved by the inclusion of various surfactant monomers to produce associative copolymer thickening properties. These "associative thickeners" (polymers comprising associative monomers) have found use in materials such as lattices used as carpet and textile backing adhesives and in similar applications. Such copolymers are described in U.S. Pat. No. 5,013,789, issued May 7, 1991, to Barron, etal. Surfactant monomers suitable for making these associative copolymer thickeners are disclosed in U.S. Pat. No. 5,011,978, issued Apr. 30, 1991, to Barron, et al.
Other surfactant monomers and copolymers prepared from such monomers which are characterized by associative thickening properties are disclosed in U.S. Pat. No. 4,743,698, issued May 10, 1988, to Ruffner, et al., and U.S. Pat. No. 4,600,761, issued Jul. 15, 1986, to Ruffner, et al. The Ruffner monomers are copolymers prepared from an urethane reaction product of a non-ionic monohydric surfactant or a sorbitan fatty ester. The Barron monomer and copolymers are derived from the reaction product of a non-ionic amine-containing surfactant with an unsaturated isocyanate. When preparing copolymers of these monomers with acrylic acid, the urea (or urethane) monomer is incorporated into the backbone of the polymer along with the comonomers.
An associative thickener copolymer disclosed in U.S. Pat. No. 4,514,552, issued Apr. 30,, 1985, to Shay, et al., and reissued as Re33,156, Jan. 30, 1990, to Shay, et al., comprises an acrylic backbone, together with urethane side chains modified with poly(alkoxy) (surfactant) moieties. The surfactant moieties contain C.sub.6 -C.sub.22 alkyl or C.sub.8 -C.sub.22 aryl terminal groups to provide hydrophobicity to the side chains. A propoxylated alkali-soluble thickener disclosed in U.S. Pat. No. 5,191,051, issued Mar. 2, 1993 to Shay, et al., is an aqueous emulsion copolymer comprising about 0.5 to 40 weight percent of a monoethylenically unsaturated, hydrophobic nonionic monomer which is the reaction product of a monohydric or monoamine-terminated polypropoxylated or polybutoxylated hydrophobe with a monoethylenically unsaturated monomer having a single group which is reactive under the conditions employed, and provided said monoethylenically unsaturated, hydrophobic nonionic monomer is not the reaction product of a monohydric or monoamine-terminated polyethoxylated hydrophobe with a monoethylenically unsaturated monomer having a single group which is reactive under the conditions employed.
Other polymers having associative thickening properties are disclosed in U.S. Pat. Nos. 4,792,343, issued Dec. 20, 1988, to Hawe, et al.; 4,384,096, issued May 17, 1983, to Sonnabend; 3,657,175, issued Apr. 18, 1972, to Zimmerman; and 5,102,936, issued Apr. 7, 1992, to Huth, et al.
It has now been discovered that a variety of polymeric materials having superior associative thickening efficiency may be prepared from the novel nonionic urethane monomers of this invention. As a further benefit, these polymers have lower volatile organic compound residues than polymers known in the art for thickening compositions such as carpet backing adhesives. In one aspect, the monomer is the reaction product of approximately equimolar amounts of selected non-ionic, monohydric surfactants and a monoethylenically unsaturated isocyanate which reaction product may subsequently be polymerized to yield a polymer backbone comprising urethane moieties. In another aspect of this invention, selected non-ionic, multihydric surfactants are reacted with approximately two moles of a monoethylenically unsaturated isocyanate to provide a multifunctional monomer having associative thickening potential, as well as potential for crosslinking polymers so as to further enhance thickening efficiency.
As used herein the term "thickening efficiency" refers to the relative increase in viscosity or thickening effect produced by the addition of a minimum amount of a thickening agent of this invention to an aqueous system, e.g., an aqueous dispersion of a polymeric material or other insoluble materials, with that produced by a same amount of another thickening agent.
Such monomers may be advantageously produced from surfactants comprising poly(ethylene oxide)(butylene oxide) block C.sub.1 -C.sub.4 alkoxy-terminated chains in lieu of the C.sub.6 -C.sub.30 hydrocarbon terminal groups that have been traditionally used as the hydrophobe in associative monomers. Thus, the monomers of this invention surprisingly provide associative thickening properties to their acrylic copolymers in the absence of the hydrophobic moieties used in the prior art.
In addition to unexpected thickening efficiencies, the polymers prepared from the monomers herein provide a variety of benefit in applications such as carpet backing adhesives, including a reduction in the volatile organic chemical content of the finished carpet and improve adhesive tensile strength and froth stability, relative to conventional thickeners.